Tanah lempung memiliki tanah berbutir halus koloidal dan kandungan air yang cukup banyak di dalam tanah lempung ini menyebabkan daya dukung tanah terhadap struktur yang dibangun di atasnya sangat rendah. Untuk memperbaiki sifat dari tanah maka dilakukan stabilisasi kimiawi dengan menggunakan abu cangkang sawit yang ditinjau dari sifat fisik melalui pengujian CBR. Penggunaan abu cangkang sawit diambil dengan variasi masing-masing 5%, 10%, 15% dan 20%. Dari variasi campuran abu cangkang sawit, didapatkan nilai penambahan abu cangkang sawit. Tanah Asli dengan nilai kadar air 44.8276%, Gs = 2.4798, LL = 52.1571%, PL= 32.5390%, IP= 19.6181%, SL= 11.8654%, pemadatan = 2.7242 gr/cm3 dan CBR= 2.4000% dan memiliki jenis tanah lempung. Tanah asli di stabilisasi dengan campuran abu cangkang sawit sebesar 10% pada variasi kedua yang memberikan perbedaan hasil dari tanah asli dengan nilai kadar air = 29.4939%, Gs =2.3007, LL = 33.1856%, PL= 24.3725%, IP= 8.8131%, SL= 3.7770%, mengalami kenaikan pada pemadatan menjadi 1.3831 gr/cm3 dan CBR 8.5000%.

Clay soils have colloidal fine-grained soils and a large amount of water content in this clay causes the carrying capacity of the soil to the structure built on it is very low. To improve the properties of the soil, chemical stabilization was carried out using palm shell ash which was viewed from the physical properties through CBR testing. The use of palm shell ash was taken with a variation of 5% each. 10%, 15% and 20%. From the variation of the mixture of palm shell ash, the optimum percentage value for the addition of palm shell ash was. Original Soil with a moisture content of 44,8276%, Gs = 2.4798 LL= 52.1571 %, PL= 32.5390%, IP=19.6181%, SL= 11.8654%. compaction = 2.7242 gr/cm³ and CBR=2.4000% and has clay type. The original soil was stabilized with a mixture of 20% palm shell ash in the second variation which gave the difference in yield from the original soil with a moisture content value = 29.4939%, Gs = 2.3007, LL = 33.1858%, PL = 24.3725 %, IP = 8.8131%, SL = 3.7770%, an increase in compaction to 1.3831 gr/cm3 and CBR 8.5000%.